High-density polyethylene compositions, method of making the same, injection molded articles made therefrom, and method of making such articles

ABSTRACT

The instant invention is a high-density polyethylene composition, method of producing the same, injection molded articles made therefrom, and method of making such articles. The high-density polyethylene composition of the instant invention includes a first component, and a second component. The first component is a high molecular weight ethylene alpha-olefin copolymer having a density in the range of 0.920 to 0.946 g/cm3, and a melt index (I21.6) in the range of 1 to 15 g/10 minutes. The second component is a low molecular weight ethylene polymer having a density in the range of 0.965 to 0.980 g/cm3, and a melt index (I2) in the range of 30 to 1500 g/10 minutes. The high-density polyethylene composition has a melt index (I2) of at least 1, a density in the range of 0.950 to 0.960 g/cm3. The method of producing a high-density polyethylene composition includes the following steps: (1) introducing ethylene, and one or more alpha-olefin comonomers into a first reactor; (2) (co)polymerizing the ethylene in the presence of one or more alpha-olefin comonomers in the first reactor thereby producing a first component, wherein the first component being a high molecular weight ethylene alpha-olefin copolymer having a density in the range of 0.920 to 0.946 g/cm3, and a melt index (I21.6) in the range of 1 to 15 g/10 minutes; (3) introducing the first component and additional ethylene into a second reactor; (4) polymerizing the additional ethylene in the second reactor thereby producing a second component, wherein the second component being a low molecular weight ethylene polymer having a density in the range of 0.965 to 0.980 g/cm3, and a melt index (I2) in the range of 30 to 1500 g/10 minutes; and (5) thereby producing the high-density polyethylene composition, wherein the high-density polyethylene composition having a melt index (I2) of at least 1, a density in the range of 0.950 to 0.960 g/cm3. The injection molded articles according to instant invention comprise the above-described inventive high-density polyethylene composition, and such articles are made via injection molding.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a non-provisional application claiming priority fromthe U.S. Provisional Patent Application Ser. No. 60/927,176, filed onMay 2, 2007 entitled “High-Density Polyethylene Compositions, Method ofMaking the Same, Injection Molded Articles Made Therefrom, and Method ofMaking Such Articles,” the teachings of which are incorporated herein asif reproduced in full hereinbelow.

FIELD OF INVENTION

The instant invention relates to high-density polyethylene compositions,method of producing the same, and injection molded articles madetherefrom, and method of making such articles.

BACKGROUND OF THE INVENTION

The use of polymeric materials to manufacture molded articles, such asclosure devices, is generally known. Different methods may be employedto manufacture closure devices, e.g. bottle caps. For example, suchclosure devices may be manufactured via compression molding or injectionmolding processes.

In compression molding process, a two-piece mold provides a cavityhaving the shape of a desired molded article. The mold is heated. Anappropriate amount of molten molding compound from an extruder is loadedinto the lower half of the mold. The two parts of the mold are broughttogether under pressure. The molding compound, softened by heat, isthereby welded into a continuous mass having the shape of the cavity. Ifthe molding compound is a thermosetting material, the continuous massmay be hardened via further heating, under pressure, in the mold. If themolding compound is a thermoplastic material, the continuous mass may behardened via chilling, under pressure, in the mold.

In injection molding process, molding compound is fed into an extrudervia a hopper. The extruder conveys, heats, melts, and pressurizes themolding compound to a form a molten stream. The molten stream is forcedout of the extruder through a nozzle into a relatively cool mold heldclosed under pressure thereby filing the mold. The melt cools andhardens until fully set-up. The mold then opens and the molded part isremoved.

In general, a closure device, e.g. a soda bottle cap, should be strongenough to withstand the pressure of a carbonated drink, and yet softenough to provide an excellent seal on the bottle without the need foran inner liner. Additionally, a closure device, e.g. a soda bottle cap,should generally possess good environmental stress crack resistance,good impact strength, good removal torque, and good strip torque.Different techniques have been employed to provide for such closuredevices having acceptable properties.

For example, the use of a polypropylene polymer as a bottle cap closurefor the needed strength with an inner liner, which may be comprised ofsoft ethylene/vinyl acetate (EVA), polyvinyl chloride (PVC), butylrubber, etc., is also generally well known. However, this two-partconstruction is costly because of the need for an inner liner.Furthermore, it would be easier and more convenient to use a one-piececlosure, without a liner. Additionally, customers are always looking forimproved shrinkage behavior. All polymers undergo shrinkage from themelt to the solid. Improved shrinkage is defined as consistently thesame and having a tight tolerance, especially when various colors areused. In the instant invention, the polymer composition in eithernatural or colored form provides improved consistency as defined as alower standard deviation of flow direction shrinkage as a percentage ofthe mean shrinkage across multiple colored (and natural) parts. Thishelps customers in that parts having too low or too high shrinkage arenot made leading to lower scrap rates. Furthermore, addition ofnucleators, potassium stearate or Milliken HPN-20E, reduce this standarddeviation further and are therefore more preferred.

In attempts to eliminate the need for a two-part construction, the useof different blends of polymers has been suggested. However, there isstill a need for polymer formulations that can be injection molded intoclosure devices having acceptable properties, such as no need for linersto facilitate a seal, acceptable taste and odor, satisfactory stresscrack resistance, and impact strength to prevent cap failure.

SUMMARY OF THE INVENTION

The instant invention is a high-density polyethylene composition, methodof producing the same, injection molded articles made therefrom, andmethod of making such articles. The high-density polyethylenecomposition of the instant invention includes a first component, and asecond component. The first component is a high molecular weightethylene alpha-olefin copolymer having a density in the range of 0.920to 0.946 g/cm³, and a melt index (I_(21.6)) in the range of 1 to 15 g/10minutes. The second component is a low molecular weight ethylene polymerhaving a density in the range of 0.965 to 0.980 g/cm³, and a melt index(I₂) in the range of 30 to 1500 g/10 minutes. The high-densitypolyethylene composition has a melt index (I₂) of at least 1, a densityin the range of 0.950 to 0.960 g/cm³. The method of producing ahigh-density polyethylene composition includes the following steps: (1)introducing ethylene, and one or more alpha-olefin comonomers into afirst reactor; (2) (co)polymerizing the ethylene in the presence of oneor more alpha-olefin comonomers in the first reactor thereby producing afirst component, wherein the first component being a high molecularweight ethylene alpha-olefin copolymer having a density in the range of0.920 to 0.946 g/cm³, and a melt index (I_(21.6)) in the range of 1 to15 g/10 minutes; (3) introducing the first component and additionalethylene into a second reactor; (4) polymerizing the additional ethylenein the second reactor thereby producing a second component, wherein thesecond component being a low molecular weight ethylene polymer having adensity in the range of 0.965 to 0.980 g/cm³, and a melt index (I₂) inthe range of 30 to 1500 g/10 minutes; and (5) thereby producing thehigh-density polyethylene composition, wherein the high-densitypolyethylene composition having a melt index (I₂) of at least 1, adensity in the range of 0.950 to 0.960 g/cm³. The injection moldedarticles according to instant invention comprise the above-describedinventive high-density polyethylene composition, and such articles aremade via injection molding.

In one embodiment, the instant invention provides a high-densitypolyethylene composition comprising a high molecular weight polyethylenealpha-olefin copolymer having a density in the range of 0.920 to 0.946g/cm³, and a melt index (I_(21.6)) in the range of 1 to 15 g/10 minutes,and a low molecular weight ethylene polymer having a density in therange of 0.965 to 0.980 g/cm³, and a melt index (I₂) in the range of 30to 1500 g/10 minutes, wherein the inventive high-density polyethylenecomposition having a melt index (I₂) of at least 1 g/10 minutes, adensity in the range of 0.950 to 0.960 g/cm³.

In an alternative embodiment, the instant invention further provides amethod for producing a high-density polyethylene composition comprisingthe steps of: (1) introducing ethylene, and one or more alpha-olefincomonomers into a first reactor; (2) (co)polymerizing the ethylene inthe presence of one or more alpha-olefin comonomers in the first reactorthereby producing a high molecular weight ethylene alpha-olefincopolymer having a density in the range of 0.920 to 0.946 g/cm³, and amelt index (I₂₁) in the range of 1 to 15 g/10 minutes; (3) introducingthe high molecular weight ethylene alpha-olefin copolymer and additionalethylene into a second reactor; (4) polymerizing the additional ethylenein the second reactor thereby producing a low molecular weight ethylenepolymer having a density in the range of 0.965 to 0.980 g/cm³, and amelt index (I₂) in the range of 30 to 1500 g/10 minutes; and (5) therebyproducing the high-density polyethylene composition, wherein thehigh-density polyethylene composition having a melt index (I₂) of atleast 1, a density in the range of 0.950 to 0.960 g/cm³.

In another alternative embodiment, the instant invention provides aninjection molded article comprising a high-density polyethylenecomposition, wherein the high-density polyethylene compositioncomprising a high molecular weight polyethylene alpha-olefin copolymerhaving a density in the range of 0.920 to 0.946 g/cm³, and a melt index(I_(21.6)) in the range of 1 to 15 g/10 minutes, and a low molecularweight ethylene polymer having a density in the range of 0.965 to 0.980g/cm³, and a melt index (I₂) in the range of 30 to 1500 g/10 minutes,wherein the inventive high-density polyethylene composition having amelt index (I₂) of at least 1 g/10 minutes, a density in the range of0.950 to 0.960 g/cm³.

In another alternative embodiment, the instant invention provides amethod of making an article comprising the steps of: (1) providing ahigh-density polyethylene composition comprising a high molecular weightethylene alpha-olefin copolymer having a density in the range of 0.920to 0.946 g/cm³, and a melt index (I_(21.6)) in the range of 1 to 15 g/10minutes; and a low molecular weight ethylene polymer having a density inthe range of 0.965 to 0.980 g/cm³, and a melt index (I₂) in the range of30 to 1500 g/10 minutes; wherein the high-density polyethylenecomposition having a melt index (I₂) of at least 1 g/10 minutes, adensity in the range of 0.950 to 0.960 g/cm³; (2) injection molding thehigh-density polyethylene composition (3) thereby forming the article.

In an alternative embodiment, the instant invention provides a methodfor producing a high-density polyethylene composition, in accordancewith any of the preceding embodiments except that the second reactorbeing substantially free of any other alpha-olefin copolymers.

In an alternative embodiment, the instant invention provides ahigh-density polyethylene composition, method of producing the same,articles made therefrom, and method of making such articles, inaccordance with any of the preceding embodiments, except that thehigh-density polyethylene composition having a standard deviation offlow direction shrinkage of less than 7 percent across different colors.

In an alternative embodiment, the instant invention provides ahigh-density polyethylene composition, method of producing the same,articles made therefrom, and method of making such articles, inaccordance with any of the preceding embodiments, except that thehigh-density polyethylene composition having a standard deviation offlow direction shrinkage of less than 6 percent across different colors.

In an alternative embodiment, the instant invention provides ahigh-density polyethylene composition, method of producing the same,articles made therefrom, and method of making such articles, inaccordance with any of the preceding embodiments, except that thehigh-density polyethylene composition having a standard deviation offlow direction shrinkage of less than 4.5 percent across differentcolors.

In an alternative embodiment, the instant invention provides ahigh-density polyethylene composition, method of producing the same,articles made therefrom, and method of making such articles, inaccordance with any of the preceding embodiments, except that thehigh-density polyethylene composition further comprising 100 to 10,000ppm by weight of a nucleator. More preferred ranges include 200 to 5000parts per million, even more preferred 300 to 3000 parts per million,and most preferred 400 to 2000 parts per million.

In an alternative embodiment, the instant invention provides ahigh-density polyethylene composition, method of producing the same,articles made therefrom, and method of making such articles, inaccordance with any of the preceding embodiments, except that thehigh-density polyethylene composition further comprising 100 to 10,000ppm by weight of potassium stearate or HPN-20E as a nucleator, whereinthe inventive high-density polyethylene composition having a standarddeviation of flow direction shrinkage of less than 4 percent acrossdifferent colors.

In an alternative embodiment, the instant invention provides ahigh-density polyethylene composition, method of producing the same,articles made therefrom, and method of making such articles, inaccordance with any of the preceding embodiments, except that thehigh-density polyethylene composition further comprising 100 to 10,000ppm by weight of potassium stearate or HPN-20E as a nucleator, whereinthe inventive high-density polyethylene composition having a standarddeviation of flow direction shrinkage of less than 3 percent acrossdifferent colors.

In an alternative embodiment, the instant invention provides ahigh-density polyethylene composition, method of producing the same,articles made therefrom, and method of making such articles, inaccordance with any of the preceding embodiments, except that thehigh-density polyethylene composition further comprising 100 to 10,000ppm by weight of potassium stearate or HPN-20E as a nucleator, whereinthe inventive high-density polyethylene composition having a standarddeviation of flow direction shrinkage of less than 2 percent acrossdifferent colors.

In an alternative embodiment, the instant invention provides ahigh-density polyethylene composition, method of producing the same,articles made therefrom, and method of making such articles, inaccordance with any of the preceding embodiments, except that thehigh-density polyethylene composition having a 1% secant modulus in psiof equal or greater to the following relationship[(7,492,165*density(g/cm³))−6,975,000] psi/(g/cm³).

In an alternative embodiment, the instant invention provides ahigh-density polyethylene composition, method of producing the same,articles made therefrom, and method of making such articles, inaccordance with any of the preceding embodiments, except that the highmolecular weight polyethylene alpha-olefin copolymer having a density inthe range of 0.925 to 0.945 g/cm³.

In another alternative embodiment, the instant invention provides ahigh-density polyethylene composition, method of producing the same,articles made therefrom, and method of making such articles, inaccordance with any of the preceding embodiments, except that the highmolecular weight polyethylene alpha-olefin copolymer having a density inthe range of 0.928 to 0.944 g/cm³.

In another alternative embodiment, the instant invention provides ahigh-density polyethylene composition, method of producing the same,articles made therefrom, and method of making such articles, inaccordance with any of the preceding embodiments, except that the highmolecular weight polyethylene alpha-olefin copolymer having a melt index(I_(21.6)) in the range of 2 to 12 g/10 minutes.

In another alternative embodiment, the instant invention provides ahigh-density polyethylene composition, method of producing the same,articles made therefrom, and method of making such articles, inaccordance with any of the preceding embodiments, except that the highmolecular weight polyethylene alpha-olefin copolymer having a melt index(I_(21.6)) in the range of 2.5 to 11 g/10 minutes.

In another alternative embodiment, the instant invention provides ahigh-density polyethylene composition, method of producing the same,articles made therefrom, and method of making such articles, inaccordance with any of the preceding embodiments, except that the lowmolecular weight ethylene polymer having a density in the range of 0.965to 0.975 g/cm³.

In another alternative embodiment, the instant invention provides ahigh-density polyethylene composition, method of producing the same,articles made therefrom, and method of making such articles, inaccordance with any of the preceding embodiments, except that the lowmolecular weight ethylene polymer having a melt index (I₂) in the rangeof 40 to 1300 g/10 minutes.

In another alternative embodiment, the instant invention provides ahigh-density polyethylene composition, method of producing the same,articles made therefrom, and method of making such articles, inaccordance with any of the preceding embodiments, except that the lowmolecular weight ethylene polymer having a melt index (I₂) in the rangeof 50 to 1000 g/10 minutes.

In another alternative embodiment, the instant invention provides ahigh-density polyethylene composition, method of producing the same,articles made therefrom, and method of making such articles, inaccordance with any of the preceding embodiments, except that thehigh-density polyethylene composition having a melt index (I₂) in therange of 1 to 2 g/10 minutes; or in the alternative, having a melt index(I₂) of at least 2 g/10 minutes.

In another alternative embodiment, the instant invention provides ahigh-density polyethylene composition, method of producing the same,articles made therefrom, and method of making such articles, inaccordance with any of the preceding embodiments, except that the highmolecular weight ethylene alpha-olefin copolymer having a molecularweight in the range of 150,000 to 300,000.

In another alternative embodiment, the instant invention provides ahigh-density polyethylene composition, method of producing the same,articles made therefrom, and method of making such articles, inaccordance with any of the preceding embodiments, except that the lowmolecular weight ethylene polymer having a molecular weight in the rangeof 12,000 to 45,000.

In another alternative embodiment, the instant invention provides ahigh-density polyethylene composition, method of producing the same,articles made therefrom, and method of making such articles, inaccordance with any of the preceding embodiments, except that the highmolecular weight polyethylene alpha-olefin copolymer having a density inthe range of 0.928 to 0.944 g/cm³, and a melt index (I21.6) in the rangeof 2.5 to 11 g/10 minutes, and the low molecular weight ethylene polymerhaving a density in the range of 0.965 to 0.975 g/cm³, and a melt index(I₂) in the range of 50 to 1000 g/10 minutes.

In another alternative embodiment, the instant invention provides ahigh-density polyethylene composition, method of producing the same,articles made therefrom, and method of making such articles, inaccordance with any of the preceding embodiments, except that both thehigh molecular weight polyethylene alpha-olefin copolymer and the lowmolecular weight ethylene polymer being substantially free of any longchain branching.

In another alternative embodiment, the instant invention provides ahigh-density polyethylene composition, method of producing the same,articles made therefrom, and method of making such articles, inaccordance with any of the preceding embodiments, except that thehigh-density polyethylene composition being substantially free of anylong chain branching.

In another alternative embodiment, the instant invention provides ahigh-density polyethylene composition, method of producing the same,articles made therefrom, and method of making such articles, inaccordance with any of the preceding embodiments, except that thehigh-density polyethylene composition having a single ATREF temperaturepeak, wherein the ATREF temperature peak having a temperature peakmaximum between about 90° C. to about 105° C.; and wherein calculatedpurge fraction in the range of less than 15.5 percent.

In another alternative embodiment, the instant invention provides anarticle and a method of making such an article, in accordance with anyof the preceding embodiments, except that the article having anenvironmental stress crack resistance of at least 10 hours measured viaASTM D-1693 condition B, 10% Igepal, or at least 100 hours measured viaASTM D-1693 condition B, 100% Igepal.

In another alternative embodiment, the instant invention provides anarticle and a method of making such an article, in accordance with anyof the preceding embodiments, except that the article being a closuredevice.

In another alternative embodiment, the instant invention provides aninjection molded article and a method of making such an article, inaccordance with any of the preceding embodiments, except that thearticle being a bottle cap.

In another alternative embodiment, the instant invention provides aninjection molded article and a method of making such an article, inaccordance with any of the preceding embodiments, except that thearticle being a cap including a skirt that axially extends from theperiphery of a base, and having internal threads for securing the cap toa container.

BRIEF DESCRIPTION OF THE DRAWINGS

For the purpose of illustrating the instant invention, there is shown inthe drawings a form that is presently preferred; it being understood,however, that this invention is not limited to the precise arrangementsand instrumentalities shown.

FIG. 1 is a graph illustrating how the calculated ATREF high-densityfraction and purge fraction of the high molecular weight polyethylenecomponent of the inventive Example 1 was determined.

FIG. 2 is a graph illustrating how the calculated ATREF high-densityfraction and purge fraction of the high molecular weight polyethylenecomponent of the inventive Example 2 was determined.

FIG. 3 is a graph illustrating how the calculated ATREF high-densityfraction and purge fraction of the high molecular weight polyethylenecomponent of the inventive Example 3 was determined.

FIG. 4 is a graph illustrating how the calculated ATREF high-densityfraction and purge fraction of the high molecular weight polyethylenecomponent of the inventive Example 4 was determined.

FIG. 5 is a graph illustrating how the calculated ATREF high-densityfraction and purge fraction of the high molecular weight polyethylenecomponent of the inventive Example 5 was determined.

FIG. 6 is a graph illustrating how the calculated ATREF high-densityfraction and purge fraction of the high molecular weight polyethylenecomponent of the inventive Example 6 was determined.

FIG. 7 is a graph illustrating the relationship between the density ing/cm³ and 1% secant modulus in psi, where the inventive high-densitypolyethylene composition having a 1% secant modulus in psi of equal orgreater to the following relationship:[(7,492,165*density(g/cm³))−6,975,000] psi(g/cm³).

DETAILED DESCRIPTION OF THE INVENTION

The high-density polyethylene composition of the instant inventionincludes a first component, and a second component. The first componentis preferably a high molecular weight ethylene alpha-olefin copolymerhaving a density in the range of 0.920 to 0.946 g/cm³, and a melt index(I₂₁) of 1 to 15 g/10 minutes. The second component is preferably a lowmolecular weight ethylene polymer having a density in the range of 0.965to 0.980 g/cm³, and a melt index (I₂) in the range of 30 to 1500 g/10minutes. The high-density polyethylene composition has a melt index (I₂)of at least 1 g/10 minutes, a density in the range of 0.950 to 0.960g/cm³. The high-density polyethylene composition may further includeadditional components, additives, or adjuvants. The high-densitypolyethylene composition is a bimodal polymer, or in the alternative,the high-density polyethylene is a multimodal polymer.

The term “bimodal,” as used herein, means that the molecular weightdistribution (MWD) in a Gel Permeation Chromatography (GPC) curveexhibits two component polymers, for example, two peaks or wherein onecomponent polymer may even exist as a hump, shoulder, or tail relativeto the MWD of the other component polymer; or in the alternative, forexample, wherein the two components may have only one single peak withno bumps, shoulders, or tails.

The term “multimodal” as used herein means that the MWD in a GPC curveexhibits more than two component polymers, for example, three or morepeaks or wherein one component polymer may even exist as a hump,shoulder, or tail, relative to the MWD of the other component polymers;or in the alternative, wherein three or more components may have onlyone single pick with no bumps, shoulders, or tails.

The term “polymer” is used herein to indicate a homopolymer, aninterpolymer (or copolymer), or a terpolymer. The term “polymer,” asused herein, includes interpolymers, such as, for example, those made bythe copolymerization of ethylene with one or more C₃-C₂₀alpha-olefin(s).

The term “interpolymer,” as used herein, refers to polymers prepared bythe polymerization of at least two different types of monomers. Thegeneric term interpolymer thus includes copolymers, usually employed torefer to polymers prepared from two different types of monomers, andpolymers prepared from more than two different types of monomers.

The term (co)polymerization, as used herein, refers to polymerization ofethylene in the presence of one or more alpha-olefin comonomers.

The first component is a polymer, for example a polyolefin. The firstcomponent is preferably be an ethylene polymer; for example, the firstcomponent is preferably a high molecular weight ethylene alpha-olefincopolymer. The first component is substantially free of any long chainbranching. Substantially free of any long chain branching, as usedherein, refers to an ethylene polymer preferably substituted with lessthan about 0.1 long chain branch per 1000 total carbons, and morepreferably, less than about 0.01 long chain branch per 1000 totalcarbons. The presence of long chain branches is typically determinedaccording to the methods known in the art, such as gel permeationchromatography coupled with low angle laser light scattering detector(GPC-LALLS) and gel permeation chromatography coupled with adifferential viscometer detector (GPC-DV). The first component has adensity in the range of 0.920 to 0.946 g/cm³. All individual values andsubranges from 0.920 to 0.946 g/cm³ are included herein and disclosedherein; for example, the first component has a density in the range of0.925 to 0.945 g/cm³, or in the alternative, the first component has adensity in the range of 0.928 to 0.944 g/cm³. The first component has amelt index (I_(21.6)); in the range of 1 to 15 g/10 minutes. Allindividual values and subranges from 1 to 15 g/10 minutes are includedherein and disclosed herein; for example, the first component has a meltindex (I_(21.6)) in the range of 2 to 12 g/10 minutes, or in thealternative, the first component has a melt index (I_(21.6)) in therange of 2.5 to 11 g/10 minutes. The first component has molecularweight in the range of 150,000 to 300,000. All individual values andsubranges from 150,000 to 300,000 are included herein and disclosedherein; for example, the first component has a molecular weight in therange of 150,000 to 270,000; or in the alternative, the first componenthas a molecular weight in the range of 150,000 to 240,000. The firstcomponent may comprise any amount of one or more alpha-olefincopolymers; for example, the first component comprises about less than10 percent by weight of one or more alpha-olefin comonomers, based onthe weight of the first component. All individual values and subrangesless than 10 weight percent are included herein and disclosed herein.The first component may comprise any amount of ethylene; for example,the first component comprises at least about 90 percent by weight ofethylene, based on the weight of the first component. All individualvalues and subranges above 90 weight percent are included herein anddisclosed herein; for example, the first component comprises at least 95percent by weight of ethylene, based on the weight of the firstcomponent.

The alpha-olefin comonomers typically have no more than 20 carbon atoms.For example, the alpha-olefin comonomers may preferably have 3 to 10carbon atoms, and more preferably 3 to 8 carbon atoms. Exemplaryalpha-olefin comonomers include, but are not limited to, propylene,1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene,and 4-methyl-1-pentene. The alpha-olefin comonomers are preferablyselected from the group consisting of propylene, 1-butene, 1-hexene, and1-octene, and more preferably from the group consisting of 1-hexene and1-octene.

The second component is a polymer, for example a polyolefin. The secondcomponent is preferably an ethylene polymer; for example, the secondcomponent is preferably a low molecular weight ethylene homopolymer. Theethylene homopolymer may contain trace amounts of contaminatecomonomers, e.g. alpha-olefin comonomers. The term ethylene homopolymer,as used herein, refers to an ethylene polymer containing at least 99percent by weight of ethylene units. The second component is preferablysubstantially free of any long chain branching. Substantially free ofany long chain branching, as used herein, refers to an ethylene polymerpreferably substituted with less than about 0.1 long chain branch per1000 total carbons, and more preferably, less than about 0.01 long chainbranch per 1000 total carbons. The presence of long chain branches istypically determined according to the methods known in the art, asmentioned above. The second component has a density in the range of0.965 to 0.980 g/cm³. All individual values and subranges from 0.965 to0.980 g/cm³ are included herein and disclosed herein; for example, thesecond component has a density in the range of 0.965 to 0.975 g/cm³. Thesecond component has a melt index (I₂) in the range of 30 to 1500 g/10minutes. All individual values and subranges from 30 to 1500 g/10minutes are included herein and disclosed herein; for example, thesecond component has a melt index (I₂) in the range of 40 to 1300 g/10minutes; or in the alternative, the second component has a melt index(I₂) in the range of 50 to 1000 g/10 minutes. The second component has amolecular weight in the range of 12,000 to 45,000. All individual valuesand subranges from 12,000 to 45,000 are included herein and disclosedherein; for example, the second component has a molecular weight in therange of 15,000 to 45,000; or in the alternative, the second componenthas a molecular weight in the range of 20,000 to 45,000. The secondcomponent comprises less than 1.00 percent by weight of one or moreadditional alpha-olefin copolymers, based on the weight of the secondcomponent. All individual values and subranges from less than 1.00weight percent are included herein and disclosed herein; for example,the second component may comprise about 0.0001 to about 1.00 percent byweight of one or more additional alpha-olefin copolymers; the secondcomponent may comprise about 0.001 to about 1.00 percent by weight ofone or more additional alpha-olefin copolymers; or in the alternative,the second component is free of any additional alpha-olefin copolymers.The second component comprises at least about 99 percent by weight ofethylene, based on the weight of the second component. All individualvalues and subranges from about 99 to about 100 weight percent areincluded herein and disclosed herein; for example, the second componentcomprises about 99.5 to about 100 percent by weight of ethylene, basedon the weight of the second component.

The high-density polyethylene composition has a density in the range of0.950 to 0.960 g/cm³. All individual values and subranges from 0.950 to0.960 g/cm³ are included herein and disclosed herein. The high-densitypolyethylene composition has a melt index (I₂) of at least 1 g/10minutes. All individual values and subranges equal or greater than 1g/10 minutes are included herein and disclosed herein; for example, thehigh-density polyethylene composition has a melt index (I₂) in the rangeof 1 to 2 g/10 minutes; or in the alternative, the high-densitypolyethylene composition has a melt index (I₂) of at least 2 g/10minutes. The high-density polyethylene composition is substantially freeof any long chain branching. Substantially free of any long chainbranching, as used herein, refers to a polyethylene compositionpreferably substituted with less than about 0.1 long chain branch per1000 total carbons, and more preferably, less than about 0.01 long chainbranch per 1000 total carbons. The presence of long chain branches istypically determined according to the methods known in the art, asmentioned above. The high-density polyethylene composition has amolecular weight distribution in the range of 4 to 15. All individualvalues and subranges from 4 to 15 are included herein and disclosedherein; for example, the high-density polyethylene composition has amolecular weight distribution in the range of 5 to 13; or in thealternative, the high-density polyethylene composition has a molecularweight distribution in the range of 5 to 11. The term molecular weightdistribution or “MWD,” as used herein, refers to the ratio of weightaverage molecular weight (Mw) to number average molecular weight(M_(n)), i.e. (M_(w)/M_(n)), described in further details hereinbelow.The high-density polyethylene composition has an environmental stresscrack resistance of at least 10 hours measured via ASTM D-1693,Condition B, 10% Igepal, or preferably at least 20 hours measured viaASTM D-1693, Condition B, 10% Igepal, or more preferably, at least 40hours measured via ASTM D-1693, Condition B, 10% Igepal. In thealternative, the high-density polyethylene composition has anenvironmental stress crack resistance of at least 100 hours measured viaASTM D-1693, Condition B, 100% Igepal, or preferably, at least 125 hoursmeasured via ASTM D-1693, Condition B, 100% Igepal, or more preferably,at least 150 hours measured via ASTM D-1693, Condition B, 100% Igepal.The high-density polyethylene composition may comprise any amounts offirst component, second component, or combinations thereof. Thehigh-density polyethylene composition comprises about 40 to about 65percent by weight of the first component, based on the total weight ofthe first and second components. All individual values and subrangesfrom about 40 to about 65 weight percent are included herein anddisclosed herein; for example, the high-density polyethylene compositioncomprises about 42 to about 64 percent by weight of the first component,based on the total weight of first and second components. Thehigh-density polyethylene composition further comprises about 35 toabout 60 percent by weight of the second component, based on the totalweight of the first and second components. All individual values andsubranges from about 35 to about 60 weight percent are included hereinand disclosed herein; for example, the high-density polyethylenecomposition further comprises about 36 to about 58 percent by weight ofthe second component, based on the total weight of the first and secondcomponents. Preferably, the high-density polyethylene composition has asingle ATREF temperature peak, wherein the ATREF temperature peak havinga temperature peak maximum between about 90° C. to about 105° C. Thehigh-density polyethylene composition further has a calculated purgefraction in the range of less than 15.5 percent.

The high-density polyethylene composition may further include additionalcomponents such as other polymers, adjuvants, and/or additives. Suchadjuvants or additives include, but are not limited to, antistaticagents, color enhancers, dyes, lubricants, fillers, pigments, primaryantioxidants, secondary antioxidants, processing aids, UV stabilizers,nucleators, and combinations thereof. The high-density polyethylenecomposition compromises about less than 10 percent by the combinedweight of one or more additives, based on the weight of the high-densitypolyethylene composition. All individual values and subranges from aboutless than 10 weight percent are included herein and disclosed herein;for example, the high-density polyethylene composition comprises aboutless than 5 percent by the combined weight of one or more additives,based on the weight of the high-density polyethylene composition; or inthe alternative, the high-density polyethylene composition comprisesabout less than 1 percent by the combined weight of one or moreadditives, based on the weight of the high-density polyethylenecomposition; or in another alternative, the high-density polyethylenecomposition may compromise about less than 0.5 percent by the combinedweight of one or more additives, based on the weight of the high-densitypolyethylene composition. Nucleators include, but are not limited to,potassium stearate, HPN-20E, which is commercially available fromMilliken. Antioxidants, such as Irgafos® 168 and Irganox® 1010, arecommonly used to protect the polymer from thermal and/or oxidativedegradation. Irganox® 1010 is tetrakis (methylene(3,5-di-tert-butyl-4hydroxyhydrocinnamate), which is commerciallyavailable from Ciba Geigy Inc. Irgafos® 168 is tris (2,4di-tert-butylphenyl) phosphite, which is commercially available fromCiba Geigy Inc.

The inventive high-density polyethylene composition may further beblended with other polymers. Such other polymers are generally known toa person of ordinary skill in the art. Blends comprising the inventivehigh-density polyethylene composition is formed via any conventionalmethods. For example, the selected polymers are melt blended via asingle or twin screw extruder, or a mixer, e.g. a Banbury mixer, a Haakemixer, a Barbender internal mixer.

In general, blends containing the inventive high-density polyethylenecomposition comprises at least 40 percent by weight of the inventivehigh-density polyethylene composition, based on the total weight of theblend. All individual values and subranges in the range of at least 40weight percent are included herein and disclosed herein; for example,the blend comprises at least 50 percent by weight of the inventivehigh-density polyethylene composition, based on the total weight of theblend; or in the alternative, the blend comprises at least 60 percent byweight of the inventive high-density polyethylene composition, based onthe total weight of the blend; or in the alternative, the blendcomprises at least 70 percent by weight of the inventive high-densitypolyethylene composition, based on the total weight of the blend; or inthe alternative, the blend comprises at least 80 percent by weight ofthe inventive high-density polyethylene composition, based on the totalweight of the blend; or in the alternative, the blend comprises at least90 percent by weight of the inventive high-density polyethylenecomposition, based on the total weight of the blend; or in thealternative, the blend comprises at least 95 percent by weight of theinventive high-density polyethylene composition, based on the totalweight of the blend; or in the alternative, the blend comprises at least99.99 percent by weight of the inventive high-density polyethylenecomposition, based on the total weight of the blend.

Different polymerization reactions and catalyst systems may be employedto produce the inventive high-density polyethylene composition. Typicaltransition metal catalyst systems used to prepare the high-densitypolyethylene composition are magnesium/titanium based catalyst systems,exemplified by the catalyst system described in U.S. Pat. No. 4,302,565;vanadium based catalyst systems, such as those described in U.S. Pat.Nos. 4,508,842; 5,332,793; 5,342,907; and 5,410,003; and a metallocenecatalyst system, such as those described in U.S. Pat. Nos. 4,937,299;5,317,036; and 5,527,752. Catalyst systems that use molybdenum oxides onsilica-alumina supports are also useful. Preferred catalyst systems forpreparing the components for the inventive high-density polyethylenecomposition are Ziegler-Natta catalyst systems and metallocene catalystsystems.

In some embodiments, preferred catalysts used in the process to make thehigh-density polyethylene compositions are of the magnesium/titaniumtype. In particular, for the gas phase polymerizations, the catalyst ismade from a precursor comprising magnesium and titanium chlorides in anelectron donor solvent. This solution is often either deposited on aporous catalyst support, or a filler is added, which, on subsequentspray drying, provides additional mechanical strength to the particles.The solid particles from either support methods are often slurried in adiluent producing a high viscosity mixture, which is then used ascatalyst precursor. Exemplary catalyst types are described in U.S. Pat.Nos. 6,187,866 and 5,290,745, the entire contents of both of which areherein incorporated by reference. Precipitated/crystallized catalystsystems, such as those described in U.S. Pat. Nos. 6,511,935 and6,248,831, the entire contents of both of which are herein incorporatedby reference, may also be used. Such catalysts may further be modifiedwith one precursor activator. Such further modifications are describedin US patent publication No.: US2006/0287445 A1.

Preferably the catalyst precursor has the formula Mg_(d)Ti(OR)_(e) X_(f)(ED)_(g) wherein R is an aliphatic or aromatic hydrocarbon radicalhaving 1 to 14 carbon atoms or COR′ wherein R′ is a aliphatic oraromatic hydrocarbon radical having 1 to 14 carbon atoms; each OR groupis the same or different; X is independently chlorine, bromine oriodine; ED is an electron donor; d is 0.5 to 56; e is 0, 1, or 2; f is 2to 116; and g is >2 and up to 1.5*d+3. It is prepared from a titaniumcompound, a magnesium compound, and an electron donor.

The electron donor is an organic Lewis base, liquid at temperatures inthe range of 0° C. to 200° C., in which the magnesium and titaniumcompounds are soluble. The electron donor compounds are sometimes alsoreferred to as Lewis bases. The electron donor can be an alkyl ester ofan aliphatic or aromatic carboxylic acid, an aliphatic ketone, analiphatic amine, an aliphatic alcohol, an alkyl or cycloalkyl ether, ormixtures thereof, each electron donor having 2 to 20 carbon atoms. Amongthese electron donors, the preferred are alkyl and cycloalkyl ethershaving 2 to 20 carbon atoms; dialkyl, diaryl, and alkylaryl ketoneshaving 3 to 20 carbon atoms; and alkyl, alkoxy, and alkylalkoxy estersof alkyl and aryl carboxylic acids having 2 to 20 carbon atoms. The mostpreferred electron donor is tetrahydrofuran. Other examples of suitableelectron donors are methyl formate, ethyl acetate, butyl acetate, ethylether, dioxane, di-n-propyl ether, dibutyl ether, ethanol, 1-butanol,ethyl formate, methyl acetate, ethyl anisate, ethylene carbonate,tetrahydropyran, and ethyl propionate.

While a large excess of electron donor may be used initially to providethe reaction product of titanium compound and electron donor, the finalcatalyst precursor contains approximately 1 to approximately 20 moles ofelectron donor per mole of titanium compound and preferablyapproximately 1 to approximately 10 moles of electron donor per mole oftitanium compound.

Since the catalyst will act as a template for the growth of the polymer,it is essential that the catalyst precursor be converted into a solid.It is also essential that the resultant solid has the appropriateparticle size and shape to produce polymer particles with relativelynarrow size distribution, low amounts of fines and good fluidizationcharacteristics. Although this solution of Lewis Base, magnesium andtitanium compounds may be impregnated into a porous support and dried toform a solid catalyst; it is preferred that the solution be convertedinto a solid catalyst via spray drying. Each of these methods thus formsa “supported catalyst precursor.”

The spray dried catalyst product is then preferentially placed into amineral oil slurry. The viscosity of the hydrocarbon slurry diluent issufficiently low, so that the slurry can be conveniently pumped throughthe pre-activation apparatus, and eventually into the polymerizationreactor. The catalyst is fed using a slurry catalyst feeder. Aprogressive cavity pump, such as a Moyno pump is typically used incommercial reaction systems, while a dual piston syringe pump istypically used in pilot scale reaction systems, where the catalyst flowsare less than, or equal to, 10 cm³/hour (2.78×10⁻⁹ m³/s) of slurry.

A cocatalyst, or activator, is also fed to the reactor to effect thepolymerization. Complete activation by additional cocatalyst is requiredto achieve full activity. The complete activation normally occurs in thepolymerization reactor, although the techniques taught in EP 1,200,483may also be used.

The cocatalysts, which are reducing agents, conventionally used, arecomprised of aluminum compounds, but compounds of lithium, sodium andpotassium, alkaline earth metals, as well as compounds of other earthmetals than aluminum are possible. The compounds are usually hydrides,organometal or halide compounds. Butyl lithium and dibutyl magnesium areexamples of useful compounds of other than aluminum.

An activator compound, which is generally used with any of the titaniumbased catalyst precursors, can have the formula AlR_(a)X_(b)H_(c),wherein each X is independently chlorine, bromine, iodine, or OR′; eachR and R′ is independently a saturated aliphatic hydrocarbon radicalhaving 1 to 14 carbon atoms; b is 0 to 1.5; c is 0 or 1; and a+b+c=3.Preferred activators include alkylaluminum mono- and dichlorides,wherein each alkyl radical has 1 to 6 carbon atoms and thetrialkylaluminums Examples are diethylaluminum chloride andtri-n-hexylaluminum. About 0.10 to 10 moles, and preferably 0.15 to 2.5moles, of activator are used per mole of electron donor. The molar ratioof activator to titanium is in the range from 1:1 to 10:1, and ispreferably in the range from 2:1 to 5:1.

The hydrocarbyl aluminum cocatalyst can be represented by the formulaR₃Al or R₂AlX, wherein each R is independently alkyl, cycloalkyl, aryl,or hydrogen; at least one R is hydrocarbyl; and two or three R radicalscan be joined to form a heterocyclic structure. Each R, which is ahydrocarbyl radical, can have 1 to 20 carbon atoms, and preferably has 1to 10 carbon atoms. X is a halogen, preferably chlorine, bromine, oriodine. Examples of hydrocarbyl aluminum compounds are as follows:triisobutylaluminum, tri-n-hexylaluminum, di-isobutyl-aluminum hydride,dihexylaluminum hydride, di-isobutylhexylaluminum, isobutyldihexylaluminum, trimethylaluminum, triethylaluminum, tripropylaluminum,triisopropylaluminum, tri-n-butylaluminum, trioctylaluminum,tridecylaluminum, tridodecylaluminum, tribenzylaluminum,triphenylaluminum, trinaphthylaluminum, tritolylaluminum,dibutylaluminum chloride, diethylaluminum chloride, and ethylaluminumsesquichloride. The cocatalyst compounds can also serve as activatorsand modifiers.

Activators can be added to the precursor either before and/or duringpolymerization. In one procedure, the precursor is fully activatedbefore polymerization. In another procedure, the precursor is partiallyactivated before polymerization, and activation is completed in thereactor. Where a modifier is used instead of an activator, the modifiersare usually dissolved in an organic solvent such as isopentane and,where a support is used, impregnated into the support followingimpregnation of the titanium compound or complex, after which thesupported catalyst precursor is dried. Otherwise, the modifier solutionis added by itself directly to the reactor. Modifiers are similar inchemical structure and function to the activators as are cocatalysts.For variations, see for example, U.S. Pat. No. 5,106,926, incorporatedherein by reference in its entirety. The cocatalyst is preferably addedseparately neat or as a solution in an inert solvent, such asisopentane, to the polymerization reactor at the same time as the flowof ethylene is initiated.

In those embodiments that use a support, the precursor is supported onan inorganic oxide support such as silica, aluminum phosphate, alumina,silica/alumina mixtures, silica that has been modified with anorganoaluminum compound such as triethyl aluminum, and silica modifiedwith diethyl zinc. In some embodiments silica is a preferred support. Atypical support is a solid, particulate, porous material essentiallyinert to the polymerization. It is used as a dry powder having anaverage particle size of 10 to 250 μm and preferably 30 to 100 μm; asurface area of at least 200 m²/g and preferably at least 250 m²/g; anda pore size of at least 100×10⁻¹⁰ m and preferably at least 200×10⁻¹⁰ m.Generally, the amount of support used is that which will provide 0.1 to1.0 millimole of titanium per gram of support and preferably 0.4 to 0.9millimole of titanium per gram of support. Impregnation of the abovementioned catalyst precursor into a silica support can be accomplishedby mixing the precursor and silica gel in the electron donor solvent orother solvent followed by solvent removal under reduced pressure. When asupport is not desired, the catalyst precursor can be used in liquidform.

In another embodiment, metallocene catalysts, single-site catalysts andconstrained geometry catalysts may be used in the practice of theinvention. Generally, metallocene catalyst compounds include half andfull sandwich compounds having one or more π-bonded ligands includingcyclopentadienyl-type structures or other similar functioning structuresuch as pentadiene, cyclooctatetraendiyl and imides. Typical compoundsare generally described as containing one or more ligands capable ofπ-bonding to a transition metal atom, usually, cyclopentadienyl derivedligands or moieties, in combination with a transition metal selectedfrom Group 3 to 8, preferably 4, 5 or 6 or from the lanthanide andactinide series of the Periodic Table of Elements.

Exemplary of metallocene-type catalyst compounds are described in, forexample, U.S. Pat. Nos. 4,530,914; 4,871,705; 4,937,299; 5,017,714;5,055,438; 5,096,867; 5,120,867; 5,124,418; 5,198,401; 5,210,352;5,229,478; 5,264,405; 5,278,264; 5,278,119; 5,304,614; 5,324,800;5,347,025; 5,350,723; 5,384,299; 5,391,790; 5,391,789; 5,399,636;5,408,017; 5,491,207; 5,455,366; 5,534,473; 5,539,124; 5,554,775;5,621,126; 5,684,098; 5,693,730; 5,698,634; 5,710,297; 5,712,354;5,714,427; 5,714,555; 5,728,641; 5,728,839; 5,753,577; 5,767,209;5,770,753 and 5,770,664; European publications: EP-A-0 591 756; EP-A-0520 732; EP-A-0 420 436; EP-A-0 485 822; EP-A-0 485 823; EP-A-0 743 324;EP-A-0 518 092; and PCT publications: WO 91/04257; WO 92/00333; WO93/08221; WO 93/08199; WO 94/01471; WO 96/20233; WO 97/15582; WO97/19959; WO 97/46567; WO 98/01455; WO 98/06759 and WO 98/011144. All ofthese references are incorporated herein, in their entirety, byreference.

Suitable catalysts for use herein, preferably include constrainedgeometry catalysts as disclosed in U.S. Pat. Nos. 5,272,236 and5,278,272, which are both incorporated, in their entirety, by reference.

The monocyclopentadienyl transition metal olefin polymerizationcatalysts taught in U.S. Pat. No. 5,026,798, the teachings of which areincorporated herein by reference, are also suitable as catalysts of theinvention.

The foregoing catalysts may be further described as comprising a metalcoordination complex comprising a metal of groups 3-10 or the Lanthanideseries of the Periodic Table of the Elements, and a delocalized n-bondedmoiety, substituted with a constrain-inducing moiety. Such a complex hasa constrained geometry about the metal atom. The catalyst furthercomprises an activating cocatalyst.

Any conventional ethylene homopolymerization or (co)polymerizationreactions may be employed to produce the inventive high-densitypolyethylene composition. Such conventional ethylene homopolymerizationor (co)polymerization reactions include, but are not limited to, gasphase polymerization, slurry phase polymerization, liquid phasepolymerization, and combinations thereof using conventional reactors,e.g. gas phase reactors, loop reactors, stirred tank reactors, and batchreactors in series, or in series and parallel. The polymerization systemof the instant invention is a dual sequential polymerization system or amulti-sequential polymerization system. Examples of dual sequentialpolymerization system include, but are not limited to, gas phasepolymerization/gas phase polymerization; gas phase polymerization/liquidphase polymerization; liquid phase polymerization/gas phasepolymerization; liquid phase polymerization/liquid phase polymerization;slurry phase polymerization/slurry phase polymerization; liquid phasepolymerization/slurry phase polymerization; slurry phasepolymerization/liquid phase polymerization; slurry phasepolymerization/gas phase polymerization; and gas phasepolymerization/slurry phase polymerization. The multi-sequentialpolymerization systems includes at least three polymerization reactions.The catalyst system, described above, may also be a conventionalcatalyst system. The inventive high-density polyethylene composition ispreferably produced via a dual gas phase polymerization process, e.g.gas phase polymerization/gas phase polymerization; however, the instantinvention is not so limited, and any of the above combinations may beemployed.

In production, a dual sequential polymerization system connected inseries, as described above, may be used. The first component, i.e. thehigh molecular weight ethylene polymer, can be produced in the firststage of the dual sequential polymerization system, and the secondcomponent, i.e. the low molecular weight ethylene polymer, can beprepared in the second stage of the dual sequential polymerizationsystem. Alternatively, the second component, i.e. the low molecularweight ethylene polymer, can be made in the first stage of the dualsequential polymerization system, and the first component, i.e. the highmolecular weight ethylene polymer, can be made in the second stage ofthe dual sequential polymerization system.

For purposes of the present disclosure, the reactor, in which theconditions are conducive to making the first component is known as thefirst reactor. Alternatively, the reactor in which the conditions areconducive to making the second component is known as the second reactor.

In production, a catalyst system including a cocatalyst, ethylene, oneor more alpha-olefin comonomers, hydrogen, and optionally inert gasesand/or liquids, e.g. N₂, isopentane, and hexane, are continuously fedinto a first reactor, which is connected to a second reactor in series;the first component/active catalyst mixture is then continuouslytransferred, for example, in batches from the first reactor to thesecond reactor. Ethylene, hydrogen, cocatalyst, and optionally inertgases and/or liquids, e.g. N₂, isopentane, hexane, are continuously fedto the second reactor, and the final product, i.e. the inventivehigh-density polyethylene composition, is continuously removed, forexample, in batches from the second reactor. A preferred mode is to takebatch quantities of first component from the first reactor, and transferthese to the second reactor using the differential pressure generated bya recycled gas compression system. The inventive high-densitypolyethylene composition is then transferred to a purge bin under inertatmosphere conditions. Subsequently, the residual hydrocarbons areremoved, and moisture is introduced to reduce any residual aluminumalkyls and any residual catalysts before the inventive high-densitypolyethylene composition is exposed to oxygen. The inventivehigh-density polyethylene composition is then transferred to an extruderto be pelletized. Such pelletization techniques are generally known. Theinventive high-density polyethylene composition may further be meltscreened. Subsequent to the melting process in the extruder, the moltencomposition is passed through one or more active screens (positioned inseries of more than one) with each active screen having a micronretention size of from about 2 to about 400 (2 to 4×10⁻⁵ m), andpreferably about 2 to about 300 (2 to 3×10⁻⁵ m), and most preferablyabout 2 to about 70 (2 to 7×10⁻⁶ m), at a mass flux of about 5 to about100 lb/hr/in² (1.0 to about 20 kg/s/m²). Such further melt screening isdisclosed in U.S. Pat. No. 6,485,662, which is incorporated herein byreference to the extent that it discloses melt screening.

In an alternative production, a multi-sequential polymerization systemconnected in series and parallel, as described above, may be used. Inone embodiment of the instant invention, a catalyst system including acocatalyst, ethylene, one or more alpha-olefin comonomers, hydrogen, andoptionally inert gases and/or liquids, e.g. N₂, isopentane, and hexane,are continuously fed into a first reactor, which is connected to asecond reactor, wherein the second reactor is connected to a thirdreactor in series; the first component/active catalyst mixture is thencontinuously transferred, for example, in batches from the first reactorto the second reactor, and then to the third reactor. Ethylene,hydrogen, cocatalyst, and optionally inert gases and/or liquids, e.g.N₂, isopentane, and hexane, are continuously fed to the second and thirdreactors, and the final product, i.e. high-density polyethylenecomposition, is continuously removed, for example, in batches from thethird reactor. A preferred mode is to take batch quantities of firstcomponent from the first reactor, and transfer these to the secondreactor, and then take batches from the second reactor and transferthese to the third reactor in series using the differential pressuregenerated by a recycled gas compression system. Alternatively, the firstreactor may feed to both a second reactor and a third reactor inparallel, and the product from first reactor may be transferred toeither second or third reactor. The high-density polyethylenecomposition is then transferred to a purge bin under inert atmosphereconditions. Subsequently, the residual hydrocarbons are removed, andmoisture may be introduced to reduce any residual aluminum alkyls andany residual catalysts before the polymer, i.e. the inventivehigh-density polyethylene composition, is exposed to oxygen. Theinventive high-density polyethylene composition is then transferred toan extruder to be pelletized. Such pelletization techniques aregenerally known. The inventive high-density polyethylene composition mayfurther be melt screened. Subsequent to the melting process in theextruder, the molten compostion is passed through one or more activescreens (positioned in series of more than one) with each active screenhaving a micron retention size of from about 2 to about 400 (2 to 4×10⁻⁵m), and preferably about 2 to about 300 (2 to 3×10⁻⁵ m), and mostpreferably about 2 to about 70 (2 to 7×10⁻⁶ m), at a mass flux of about5 to about 100 lb/hr/int (1.0 to about 20 kg/s/m²). Such further meltscreening is disclosed in U.S. Pat. No. 6,485,662, which is incorporatedherein by reference to the extent that it discloses melt screening.

In another alternative production, the inventive high-densitypolyethylene composition may be produced from polymers made in two ormore independent reactors (each using the same or different catalyst)with post reaction blending.

In application, the inventive high-density polyethylene composition maybe used to manufacture shaped articles. Such articles may include, butare not limited to, closure devices, e.g. bottle caps. Different methodsmay be employed to manufacture articles such as bottle caps. Suitableconversion techniques include, but are not limited to, injectionmolding.

In injection molding process, the inventive high-density polyethylenecomposition is fed into an extruder via a hopper. The extruder conveys,heats, melts, and pressurizes the inventive high-density polyethylenecomposition to a form a molten stream. The molten stream is forced outof the extruder through a nozzle into a relatively cool mold held closedunder pressure thereby filling the mold. The melt cools and hardensuntil fully set-up. The mold then opens and the molded article, e.g.bottle cap, is removed. The injection molded cap may include a skirtthat axially extends from the periphery of a base, and may furtherinclude internal threads for securing the cap to a container.

Closure devices, e.g. bottle caps, including the inventive high-densitypolyethylene composition exhibit improved environmental crackresistance. Such bottle caps are adapted to withstand the pressure ofcarbonated drinks. Such bottle caps further facilitate closure, andsealing of a bottle, i.e. optimum torque provided by a machine to screwthe cap on the bottle, or unsealing a bottle, i.e. optimum torqueprovide by a person to unscrew the cap.

EXAMPLES

It is understood that the present invention is operable in the absenceof any component, which has not been specifically disclosed. Thefollowing examples are provided in order to further illustrate theinvention and are not to be construed as limiting.

Inventive Examples 1-6

Inventive Examples 1-6 were prepared according to the followingprocedures: a dual-sequential polymerization system, e.g. a first gasphase reactor and a second gas phase reactor operating in series, wasprovided. Ethylene, one or more alpha-olefin comonomers, hydrogen,catalyst, e.g. Ziegler-Natta catalyst, slurried in mineral oil, N₂, andisopentane were fed continuously into the first reactor. Subsequently, acocatalyst, e.g. triethylaluminum (TEAL), was fed continuously into thefirst reactor to activate the catalyst. The first polymerizationreaction of the ethylene in the presence of 1-hexene was carried out inthe first reactor under the conditions shown below in Table I therebyproducing first component-catalyst complex. The first component-catalystcomplex was continuously transferred to the second reactor. Additional,ethylene, hydrogen, cocatalyst, e.g. TEAL, N₂, and isopentane were fedcontinuously into the second reactor. No additional catalyst was addedto the second reactor. The second polymerization reaction of ethylenewas carried out in the second reactor under the conditions shown belowin Table I thereby producing the first component-catalyst-secondcomponent complex. The first component-catalyst-second component complexwas continuously removed from the second reactor in batches into theproduct chamber, where it was purged to remove residual hydrocarbons,and then transferred to a fiberpak drum. The fiberpak drum wascontinuously purged with humidified nitrogen. The polymer, i.e. theinventive high-density polyethylene composition, was further processedin a mixer/pelletizer. The polymer, i.e. the inventive high-densitypolyethylene composition, was melted in the mixer, and additives weredispersed therein the polymer, inventive high-density polyethylenecomposition, matrix. The inventive high-density polyethylene compositionwas extruded through a die plate, pelletized, and cooled. The resinsamples of the Inventive Examples 1-6 were tested for their propertiesfrom pellets, or were formed into testing plaques according to ASTMD-4703-00 and then were tested for their properties. Such properties areshown in Tables I and II, and FIGS. 1-6. The resin samples of theInventive Examples 1-6 were also tested for shrinkage propertiesaccording to ASTM D-955 utilizing a 60 mm×60 mm×2 mm plaques, and theresults are shown in Table IV.

Comparative Examples A

Comparative example A is a high-density polyethylene copolymer, which iscommercially available under the tradename B4020N1331 from INEOS Olefins& Polymers, USA. The resin samples of the comparative examples A weretested for their properties from pellets, or were formed into testingplaques according to ASTM D-4703-00 and then tested for theirproperties. Such properties are shown in Tables III.

Test Methods

Unless otherwise noted, the values reported herein were determinedaccording to the following test methods.

Density (g/cm³) was measured according to ASTM-D 792-03, Method B, inisopropanol. Specimens were measured within 1 hour of molding afterconditioning in the isopropanol bath at 23° C. for 8 min to achievethermal equilibrium prior to measurement. The specimens were compressionmolded according to ASTM D-4703-00 Annex A with a 5 min initial heatingperiod at about 190° C. and a 15° C./min cooling rate per Procedure C.The specimen was cooled to 45° C. in the press with continued coolinguntil “cool to the touch.”

Melt index (I₂) was measured at 190° C. under a load of 2.16 kgaccording to ASTM D-1238-03.

Melt index (I₅) was measured at 190° C. under a load of 5.0 kg accordingto ASTM D-1238-03.

Melt index (I₁₀) was measured at 190° C. under a load of 10.0 kgaccording to ASTM D-1238-03.

Melt index (I_(21.6)) was measured at 190° C. under a load of 21.6 kgaccording to ASTM D-1238-03.

Shrinkage was measured according to ASTM D-955 utilizing a 60 mm×60 mm×2mm plaques.

Weight average molecular weight (M_(w)) and number average molecularweight (M_(n)) were determined according to methods known in the artusing conventional GPC, as described herein below.

The molecular weight distributions of ethylene polymers were determinedby gel permeation chromatography (GPC). The chromatographic systemconsisted of a Waters (Millford, Mass.) 150° C. high temperature gelpermeation chromatograph, equipped with a Precision Detectors (Amherst,Mass.) 2-angle laser light scattering detector Model 2040. The 15° angleof the light scattering detector was used for calculation purposes. Datacollection was performed using Viscotek TriSEC software version 3 and a4-channel Viscotek Data Manager DM400. The system was equipped with anon-line solvent degas device from Polymer Laboratories. The carouselcompartment was operated at 140° C. and the column compartment wasoperated at 150° C. The columns used were four Shodex HT 806M 300 mm, 13um columns and one Shodex HT803M 150 mm, 12 μm column. The solvent usedwas 1,2,4 trichlorobenzene. The samples were prepared at a concentrationof 0.1 grams of polymer in 50 milliliters of solvent. Thechromatographic solvent and the sample preparation solvent contained 200μg/g of butylated hydroxytoluene (BHT). Both solvent sources werenitrogen sparged. Polyethylene samples were stirred gently at 160° C.for 4 hours. The injection volume used was 200 microliters, and the flowrate was 0.67 milliliters/min Calibration of the GPC column set wasperformed with 21 narrow molecular weight distribution polystyrenestandards, with molecular weights ranging from 580 to 8,400,000 g/mol,which were arranged in 6 “cocktail” mixtures with at least a decade ofseparation between individual molecular weights. The standards werepurchased from Polymer Laboratories (Shropshire, UK). The polystyrenestandards were prepared at 0.025 grams in 50 milliliters of solvent formolecular weights equal to, or greater than, 1,000,000 g/mol, and 0.05grams in 50 milliliters of solvent for molecular weights less than1,000,000 g/mol. The polystyrene standards were dissolved at 80° C. withgentle agitation for 30 minutes. The narrow standards mixtures were runfirst, and in order of decreasing highest molecular weight component, tominimize degradation. The polystyrene standard peak molecular weightswere converted to polyethylene molecular weights using the followingequation (as described in Williams and Ward, J. Polym. Sci., Polym.Let., 6, 621 (1968)):

Mpolyethylene=A×(Mpolystyrene)^(B),

where M is the molecular weight, A has a value of 0.41 and B is equal to1.0. The Systematic Approach for the determination of multi-detectoroffsets was done in a manner consistent with that published by Balke,Mourey, et al. (Mourey and Balke, Chromatography Polym. Chpt 12, (1992)and Balke, Thitiratsakul, Lew, Cheung, Mourey, Chromatography Polym.Chpt 13, (1992)), optimizing dual detector log results from Dow broadpolystyrene 1683 to the narrow standard column calibration results fromthe narrow standards calibration curve using in-house software. Themolecular weight data for off-set determination was obtained in a mannerconsistent with that published by Zimm (Zimm, B. H., J. Chem. Phys., 16,1099 (1948)) and Kratochvil (Kratochvil, P., Classical Light Scatteringfrom Polymer Solutions, Elsevier, Oxford, N.Y. (1987)). The overallinjected concentration used for the determination of the molecularweight was obtained from the sample refractive index area and therefractive index detector calibration from a linear polyethylenehomopolymer of 115,000 g/mol molecular weight, which was measured inreference to NIST polyethylene homopolymer standard 1475. Thechromatographic concentrations were assumed low enough to eliminateaddressing 2^(nd) Virial coefficient effects (concentration effects onmolecular weight). Molecular weight calculations were performed usingin-house software. The calculation of the number-average molecularweight, weight-average molecular weight, and z-average molecular weightwere made according to the following equations, assuming that therefractometer signal is directly proportional to weight fraction. Thebaseline-subtracted refractometer signal can be directly substituted forweight fraction in the equations below. Note that the molecular weightcan be from the conventional calibration curve or the absolute molecularweight from the light scattering to refractometer ratio. An improvedestimation of z-average molecular weight, the baseline-subtracted lightscattering signal can be substituted for the product of weight averagemolecular weight and weight fraction in equation (2) below:

$\begin{matrix}{{\left. {{{\left. {{{\left. a \right)\mspace{14mu} \overset{\_}{Mn}} = \frac{\sum\limits^{i}{Wf}_{i}}{\sum\limits^{i}\left( {{Wf}_{i}\text{/}M_{i}} \right)}}b} \right)\mspace{14mu} \overset{\_}{Mw}} = \frac{\sum\limits^{i}\left( {{Wf}_{i}*M_{i}} \right)}{\sum\limits^{i}{Wf}_{i}}}c} \right)\mspace{14mu} \overset{\_}{Mz}} = \frac{\sum\limits^{i}\left( {{Wf}_{i}*M_{i}^{2}} \right)}{\sum\limits^{i}\left( {{Wf}_{i}*M_{i}} \right)}} & (2)\end{matrix}$

Bimodality of distributions was characterized according to the weightfraction of the highest temperature peak in temperature rising elutionfractionation (typically abbreviated as “TREF”) data as described, forexample, in Wild et al., Journal of Polymer Science, Poly. Phys. Ed.,Vol. 20, p. 441 (1982), in U.S. Pat. No. 4,798,081 (Hazlitt et al.), orin U.S. Pat. No. 5,089,321 (Chum et al.), the disclosures of all ofwhich are incorporated herein by reference. In analytical temperaturerising elution fractionation analysis (as described in U.S. Pat. No.4,798,081 and abbreviated herein as “ATREF”), the composition to beanalyzed is dissolved in a suitable hot solvent (for example, 1,2,4trichlorobenzene), and allowed to crystallized in a column containing aninert support (for example, stainless steel shot) by slowly reducing thetemperature. The column was equipped with both an infra-red detector anda differential viscometer (DV) detector. An ATREF-DV chromatogram curvewas then generated by eluting the crystallized polymer sample from thecolumn by slowly increasing the temperature of the eluting solvent(1,2,4 trichlorobenzene). The ATREF-DV method is described in furtherdetail in WO 99/14271, the disclosure of which is incorporated herein byreference.

High Density Fraction (percent) was measured via analytical temperaturerising elution fractionation analysis (as described in U.S. Pat. No.4,798,081 and abbreviated herein as “ATREF”), which is described infurther details hereinafter. Analytical temperature rising elutionfractionation (ATREF) analysis was conducted according to the methoddescribed in U.S. Pat. No. 4,798,081 and Wilde, L.; Ryle, T. R.;Knobeloch, D. C.; Peat, I. R.; Determination of Branching Distributionsin Polyethylene and Ethylene Copolymers, J. Polym. Sci., 20, 441-455(1982), which are incorporated by reference herein in their entirety.The composition to be analyzed was dissolved in trichlorobenzene andallowed to crystallize in a column containing an inert support(stainless steel shot) by slowly reducing the temperature to 20° C. at acooling rate of 0.1° C./min. The column was equipped with an infrareddetector. An ATREF chromatogram curve was then generated by eluting thecrystallized polymer sample from the column by slowly increasing thetemperature of the eluting solvent (trichlorobenzene) from 20 to 120° C.at a rate of 1.5° C./min.

Branching distributions were determined via crystallization analysisfractionation (CRYSTAF); described herein below. Crystallizationanalysis fractionation (CRYSTAF) was conducted via a CRYSTAF 200 unitcommercially available from PolymerChar, Valencia, Spain. The sampleswere dissolved in 1,2,4 trichlorobenzene at 160° C. (0.66 mg/mL) for 1hr and stabilized at 95° C. for 45 minutes. The sampling temperaturesranged from 95 to 30° C. at a cooling rate of 0.2° C./min An infrareddetector was used to measure the polymer solution concentrations. Thecumulative soluble concentration was measured as the polymercrystallizes while the temperature was decreased. The analyticalderivative of the cumulative profile reflects the short chain branchingdistribution of the polymer.

The CRYSTAF temperature peak and area are identified by the peakanalysis module included in the CRYSTAF Software (Version 2001.b,PolymerChar, Valencia, Spain). The CRYSTAF peak finding routineidentifies a temperature peak as a maximum in the dW/dT curve and thearea between the largest positive inflections on either side of theidentified peak in the derivative curve. To calculate the CRYSTAF curve,the preferred processing parameters are with a temperature limit of 70°C. and with smoothing parameters above the temperature limit of 0.1, andbelow the temperature limit of 0.3.

Solubility Distribution Breadth Index (SDBI) is the statistical valuefor the breadth of the CRYSTAF method which is calculated based on thefollowing formula:

${SDBI} = {\int\sqrt[4]{{\left( {T - T_{w}} \right)^{4} \cdot {w(T)}}{dT}}}$T_(w) = ∫T ⋅ w(T)dT ∫w(T)dT = 1

wherein T is temperature, W is weight fraction, and Tw weight averagetemperature.

Long Chain Branching was determined according to the methods known inthe art, such as gel permeation chromatography coupled with low anglelaser light scattering detector (GPC-LALLS) and gel permeationchromatography coupled with a differential viscometer detector (GPC-DV).

Resin stiffness was characterized by measuring the Flexural Modulus at 5percent strain and Secant Modulii at 1 percent and 2 percent strain, anda test speed of 0.5 inch/min (13 mm/min) according to ASTM D 790-99Method B.

Tensile strength at yield and elongation at break were measuredaccording to ASTM D-638-03 employing Type IV Specimen at 2 inch/minute(50 mm/minute).

The environmental stress crack resistance (ESCR) was measured accordingto ASTM-D 1693-01, Condition B. The susceptibility of the resin tomechanical failure by cracking was measured under constant strainconditions, and in the presence of a crack accelerating agent such assoaps, wetting agents, etc. Measurements were carried out on notchedspecimens, in a 10 percent, by volume, Igepal CO-630 (vendorRhone-Poulec, N.J.) aqueous solution, maintained at 50° C., and a 100percent, by volume, Igepal CO-630 (vendor Rhone-Poulec, N.J.) aqueoussolution, maintained at 50° C. The ESCR value was reported as F₅₀, thecalculated 50 percent failure time from the probability graph, and F₀,where there are no failures in the trial.

Short chain branching distribution and comonomer content was measuredusing C₁₃ NMR, as discussed in Randall, Rev. Macromol. Chem. Chys., C29(2&3), pp. 285-297, and in U.S. Pat. No. 5,292,845, the disclosures ofwhich are incorporated herein by reference to the extent related to suchmeasurement. The samples were prepared by adding approximately 3 g of a50/50 mixture of tetrachloroethane-d2/orthodichlorobenzene that was0.025M in chromium acetylacetonate (relaxation agent) to 0.4 g sample ina 10 mm NMR tube. The samples were dissolved and homogenized by heatingthe tube and its contents to 150° C. The data was collected using a JEOLEclipse 400 MHz NMR spectrometer, corresponding to a 13C resonancefrequency of 100.6 MHz. Acquisition parameters were selected to ensurequantitative 13C data acquisition in the presence of the relaxationagent. The data was acquired using gated 1H decoupling, 4000 transientsper data file, a 4.7 sec relaxation delay and 1.3 second acquisitiontime, a spectral width of 24,200 Hz and a file size of 64K data points,with the probe head heated to 130° C. The spectra were referenced to themethylene peak at 30 ppm. The results were calculated according to ASTMmethod D5017-91.

The resin rheology was measured on the ARES I (Advanced RheometricExpansion System) Rheometer. The ARES I was a strain controlledrheometer. A rotary actuator (servomotor) applied shear deformation inthe form of strain to a sample. In response, the sample generatedtorque, which was measured by the transducer. Strain and torque wereused to calculate dynamic mechanical properties, such as modulus andviscosity. The viscoelastic properties of the sample were measured inthe melt using a 25 mm in diameter parallel plate set up, at constantstrain (5 percent) and temperature (190° C.) and N₂ purge, and as afunction of varying frequency (0.01 to 500 s⁻¹). The storage modulus,loss modulus, tan delta, and complex viscosity of the resin weredetermined using Rheometrics Orchestrator software (v. 6.5.8). Theviscosity ratio (0.1 rad·s⁻¹/100 rad·s⁻¹) was determined to be the ratioof the viscosity measured at a shear rate of 0.1 rad/s to the viscositymeasured at a shear rate of 100 rad/s.

Vinyl unsaturations were measured according to ASTM D-6248-98.

Low shear rheological characterization is performed on a RheometricsSR5000 in stress controlled mode, using a 25 mm parallel plates fixture.This type of geometry is preferred to cone and plate because it requiresonly minimal squeezing flow during sample loading, thus reducingresidual stresses.

g′ average was determined according to the following procedure. Thechromatographic system consisted of a Waters (Millford, Mass.) 150° C.high temperature chromatograph equipped with a Precision Detectors(Amherst, Mass.) 2-angle laser light scattering detector Model 2040, anIR4 infra-red detector from Polymer Char (Valencia, Spain), and aViscotek (Houston, Tex.) 150R 4-capillary viscometer. The 15-degreeangle of the light scattering detector was used for calculationpurposes. Data collection was performed using Viscotek TriSEC softwareversion 3 and a 4-channel Viscotek Data Manager DM400. The system wasequipped with an on-line solvent degas device from Polymer Laboratories.The carousel compartment was operated at 140° C. and the columncompartment was operated at 150° C. The columns used were 4 20-micronmixed-bed light scattering “Mixed A-LS” columns from PolymerLaboratories. The solvent used was 1,2,4 trichlorobenzene. The sampleswere prepared at a concentration of 0.1 grams of polymer in 50milliliters of solvent. The chromatographic solvent and the samplepreparation solvent contained 200 ppm of butylated hydroxytoluene (BHT).Both solvent sources were nitrogen sparged. Polyethylene samples werestirred gently at 160 degrees Celsius for 4 hours. The injection volumeused was 200 microliters and the flow rate was 1 milliliters/minute.

Calibration of the GPC column set was performed with 21 narrow molecularweight distribution polystyrene standards with molecular weights rangingfrom 580 to 8,400,000, and were arranged in 6 “cocktail” mixtures withat least a decade of separation between individual molecular weights.The standards were purchased from Polymer Laboratories (Shropshire, UK).The polystyrene standards were prepared at 0.025 grams in 50 millilitersof solvent for molecular weights equal to or greater than 1,000,000, and0.05 grams in 50 milliliters of solvent for molecular weights less than1,000,000. The polystyrene standards were dissolved at 80° C. withgentle agitation for 30 minutes. The narrow standards mixtures were runfirst and in order of decreasing highest molecular weight component tominimize degradation. The polystyrene standard peak molecular weightswere converted to polyethylene molecular weights using the followingequation (as described in Williams and Ward, J. Polym. Sci., Polym.Let., 6, 621 (1968)):

Mpolyethylene=A×(Mpolystyrene)^(B)

Where M is the molecular weight, A has a value of 0.43 and B is equal to1.0.

The Systematic Approach for the determination of multi-detector offsetswas done in a manner consistent with that published by Balke, Mourey,et. al. (Mourey and Balke, Chromatography Polym. Chpt 12, (1992))(Balke, Thitiratsakul, Lew, Cheung, Mourey, Chromatography Polym. Chpt13, (1992)), optimizing triple detector log (MW and IV) results from DowBroad Polystyrene 1683 to the narrow standard column calibration resultsfrom the narrow standards calibration curve using a software. Themolecular weight data for off-set determination was obtained in a mannerconsistent with that published by Zimm (Zimm, B. H., J. Chem. Phys., 16,1099 (1948)) and Kratochvil (Kratochvil, P., Classical Light Scatteringfrom Polymer Solutions, Elsevier, Oxford, N.Y. (1987)). The overallinjected concentration used for the determination of the molecularweight was obtained from the sample refractive index area and therefractive index detector calibration from a linear polyethylenehomopolymer of 115,000 molecular weight. The chromatographicconcentrations were assumed low enough to eliminate addressing 2^(nd)Virial coefficient effects (concentration effects on molecular weight).

g′ average was calculated for the samples as follow:

1. The light scattering, viscosity, and concentration detectors werecalibrated with NBS 1475 homopolymer polyethylene (or equivalentreference);

2. The light scattering and viscometer detector offsets relative to theconcentration detector was corrected as described in the calibrationsection;

3. Baselines were subtracted from the light scattering, viscometer, andconcentration chromatograms and set integration windows making certainto integrate all of the low molecular weight retention volume range inthe light scattering chromatogram that were observable from therefractometer chromatogram;

4. A linear homopolymer polyethylene Mark-Houwink reference line wasestablished by injecting a standard with a polydispersity of at least3.0, and the data file (from above calibration method), was calculatedand the intrinsic viscosity and molecular weight from the mass constantcorrected data for each chromatographic slice was recorded;

5. The HDPE sample of interest was injected and the data file (fromabove calibration method), was calculated and the intrinsic viscosityand molecular weight from the mass constant corrected data for eachchromatographic slice was recorded;

6. The homopolymer linear reference intrinsic viscosity was shifted bythe following factor: IV=IV+1/(1+2*SCB/1,000C*branch point length) whereIV is the intrinsic viscosity of the HDPE sample of interest, SCB/1,000Cwas determined from C13 NMR, and the branch point length is 2 forbutene, 4 for hexene, or 6 for octene);

7. g′ average was calculated according to the following equation.

$g^{\prime} = \frac{{{\sum\limits_{j = {{WhereM} > {40\text{,}000}}}^{HighestM}\; \left\lbrack {c_{j} \times \left( \frac{{IV}_{j}}{{IV}_{Lj}} \right)_{M}} \right\rbrack} + {\sum\limits_{j = {LowestM}}^{{WhereM} > {40\text{,}000}}c_{j}}}\;}{\sum\limits_{j = {LowestM}}^{HighestM}\; c_{j}}$

Where c is the concentration of the slice, IV is the intrinsic viscosityof the HDPE, and IV_(L) is the intrinsic viscosity of the linearhomopolymer polyethylene reference (corrected for SCB of the HDPE sampleof interest) at the same molecular weight (M). The IV ratio was assumedto be one at molecular weights less than 40,000 to account for naturalscatter in the light scattering data.

The present invention may be embodied in other forms without departingfrom the spirit and the essential attributes thereof, and, accordingly,reference should be made to the appended claims, rather than to theforegoing specification, as indicating the scope of the invention.

TABLE I Example 1 Example 2 Example 3 Example 4 Example 5 Example 6Co-Monomer Type 1-hexene 1-hexene 1-hexene 1-hexene 1-hexene 1-hexeneCatalyst Ziegler-Natta Ziegler-Natta Ziegler-Natta Ziegler-NattaZiegler-Natta Ziegler-Natta Co-Catalyst 2.5% TEAL 2.5% TEAL 2.5% TEAL2.5% TEAL 2.5% TEAL 2.5% TEAL 1^(st) Reactor Type Gas Phase Gas PhaseGas Phase Gas Phase Gas Phase Gas Phase 2^(nd) Reactor Type Gas PhaseGas Phase Gas Phase Gas Phase Gas Phase Gas Phase 1^(st) ReactionTemperature (° C.) 85 85 85 85 85 85 2^(nd) Reaction Temperature (° C.)95 110 95 95 95 95 1^(st) Reaction Pressure (psi) 348 350 349 348 350350 2^(nd) Reaction Pressure (psi) 384 399 398 394 397 398 1^(st)Reactor C₂ Partial Pressure (psi) 22.9 32.3 33.9 29.1 45.2 48.1 2^(nd)Reactor C₂ Partial Pressure (psi) 112.1 92.1 88.8 103.0 87.4 86.2 1^(st)Reactor H₂/C₂ Molar Ratio 0.090 0.145 0.146 0.145 0.207 0.203 2^(nd)Reactor H₂/C₂ Molar Ratio 1.40 1.80 1.40 0.80 0.80 1.40 1^(st) ReactorC₆/C₂ Molar Ratio 0.060 0.036 0.031 0.032 0.020 0.021 2^(nd) ReactorC₆/C₂ Molar Ratio 0.002 0.002 0.002 0.002 0.003 0.003 1^(st) ReactorIsopentane (Mole %) 10.586 9.714 4.893 10.185 9.728 9.454 2^(nd) ReactorIsopentane (Mole %) 1.117 0.971 0.976 1.046 1.055 1.005

TABLE II Example 1 Example 2 Example 3 Example 4 Example 5 Example 6Split (1^(st) reactor/2^(nd) reactor) 0.425/0.575 0.551/0.4490.520/0.480 0.450/0.550 0.581/0.419 0.640/0.360 Cocatalyst Feed Rate(cc/hr) 150/167 146/170 144/169 146/169 143/172 147/169 (1^(st)reactor/2^(nd) reactor) Production Rate (lb/hr) 23.0/30.8 29.9/24.430.1/27.6 25.1/30.4 30.0/21.6 29.9/16.7 (1^(st) reactor/2^(nd) reactor)Bed Weight (lbs) (1^(st) reactor/2^(nd) reactor)  80.7/120.8  79.6/125.2  85/122.2  81.7/111.8  79.1/114.2  79.9/122.2 FBD (lb/ft³) (1^(st)reactor/2^(nd) reactor) 12.0/15.4 12.0/15.9 12.4/14.7 12.2/13.912.0/14.0 12.2/14.9 Bed Volume (ft³) (1^(st) reactor/2^(nd) reactor)6.7/7.9 6.7/7.9 6.8/8.3 6.7/8.0 6.6/8.2 6.6/8.2 Residence Time (hr)(1^(st) reactor/2^(nd) reactor) 3.5/2.2 2.7/2.3 2.8/2.1 3.3/2.0 2.6/2.22.7/2.6 STY (lb/hr/ft³) (1^(st) reactor/2^(nd) reactor) 3.4/3.9 4.5/3.14.4/3.3 3.8/3.8 4.6/2.6 4.5/2.0 Melt index (I₂₁) (1^(ST) Component) (~)2.46 4.84 4.79 4.63 10.79 11.04 (g/10 minutes) Density (First Component)(~) (g/cm³) 0.9288 0.9358 0.9369 0.9366 0.9433 0.9430 Residual Ti (ppm)(1^(st) component/ 3.93/1.75 3.57/2.15 3.87/1.96  3.6/1.78 2.57/1.652.35/1.54 2^(nd) component) Residual Al (ppm) (1^(st) component/ 108/66.8 86.4/61.5 88.4/60.2 100.2/72.7  82.0/68.4 77.7/67.7 2^(nd)component) Al/Ti Molar Residual Ti (ppm) 49.2/68.6 43.3/52.3 41.0/55.049.7/71.0 56.6/73.7 59.1/78.4 (1^(st) component/2^(nd) component) BulkDensity (lb/ft³) Residual Ti (ppm) 18.3/24.0 18.6/24.8 18.3/22.919.0/23.0 19.5/22.7 19.2/22.7 (1^(st) component/2^(nd) component) H-DPolyethylene Composition Melt 1.6 1.5 1.4 1.5 1.6 1.6 Index (I₂) (2.16g/10 minutes) H-D Polyethylene Composition Melt 5.9 5.3 4.8 4.8 5.0 5.1Index (I₅) (5.0 g/10 minutes) H-D Polyethylene Composition Melt 89.186.4 63.0 53.2 50.9 57.7 Index (I_(21.6)) (21.6 g/10 minutes) H-DPolyethylene Composition Melt 57 58 44 36 32 36 Flow Ratio (MI₂₁/MI₂)H-D Polyethylene Composition Melt 15 16 13 11 10 11 Flow Ratio(MI₂₁/MI₅) H-D Polyethylene Composition (M_(n)) 12730 10030 11700 1467019600 13400 H-D Polyethylene Composition (M_(w)) 115750 105460 106790106710 106580 104680 H-D Polyethylene Composition (M_(w)/M_(n)) 791400579000 482600 473000 423800 463300 Atref HD Fraction (%) 83.0 83.2 79.382.0 83.2 86.7 Atref Purge fraction (%) 10.5 13.3 10.6 14.2 8.3 10.5Atref MV average 70412 77439 65518 75618 68449 70887 Atref Purge Mv78227 81700 72441 82924 73951 70948 Viscosity at 10 − 2 sec-1 10265 91108764 8294 6973 7460 Shear Rate (Pa.s) Viscosity at 10 + 2 sec-1 910 9321059 1123 1184 1102 Shear Rate (Pa.s) Ratio 10 − 2/10 + 2 11.3 9.8 8.37.4 5.9 6.8 Flexural Modulus (0.5 in/min) (psi) 227051 240071 235814239265 233248 240173 2% Secant Modulus (psi) 151884 162889 155572 160280153836 161766 1% Secant Modulus (psi) 184733 198177 189700 195254 187175196579 Tensile Strength (psi) 1716 1423 2786 3340 3707 4095 Elongationat Break (%) 931.1 698.9 583.5 754.1 917.9 1139.5 Yield Strength (psi)3500 3500 3519 3305 3694 3943 Elongation at Yield (%) 4.66 5.84 5.1090.49 7.58 9.06 ESCR Test Data 50° C.; 10% Igepal; 75 mil plaque, 282.5101.2 64.2 44.2 24.8 45 12 mil slit ( F50 hours) 50° C.; 100% Igepal; 75mil plaque, F0 > 2000 >1470 >740 242.4 146.9 151.2 12 mil slit (F50hours)

TABLE III Comparative A Melt Index (I₂) (2.16 g/10 minutes) 2.2 MeltIndex (I₅) (5.0 g/10 minutes) 7.0 Melt Index (I_(21.6)) (21.6 g/10minutes) 90.2 Melt Flow Ratio (MI₂₁/MI₂) 42 Melt Flow Ratio (MI₂₁/MI₅)12.9 Density (g/cm³) 0.9533 M_(n) 17910 M_(w) 111930 M_(w)/M_(n) 6.25Atref HD Fraction (%) 74.4 Atref Purge fraction (%) 15.8 Atref MVaverage 68498 Atref Purge Mv 76271 Viscosity at 10 − 2 sec − 1 ShearRate (Pa · s) 5100 Viscosity at 10 + 2 sec − 1 Shear Rate (Pa · s) 960Ratio 10 − 2/10 + 2 5.3 Flexural Modulus (0.5 in/min) (psi) 203238 2%Secant Modulus (psi) 131837 Comparative Example No. Comparative A 1%Secant Modulus (psi) 159092 Tensile Strength (psi) 2765 Elongation atBreak (%) 990.6 Yield Strength (psi) 3870 Elongation at Yield (%) — ESCRTest Data 50 C 10% Igepal 75 mil plaque, 12 mil slit (F50 hours) 35.2 50C 100% Igepal 75 mil plaque, 12 mil slit (F50 hours) 26.1

Shrinkage in Shrinkage in cross-flow flow direction direction after 48hours after 48 hours Example No. Color Nucleator (%) (%) Inventive 1Natural None 3.51 1.01 Inventive 1 Green None 3.65 0.96 Inventive 1 BlueNone 3.68 1.05 Inventive 2 Natural None 3.77 0.99 Inventive 2 Green None3.78 1.25 Inventive 2 Blue None 3.93 0.93 Inventive 3 Natural None 3.481.02 Inventive 3 Green None 3.59 0.83 Inventive 3 Blue None 3.65 1.05Inventive 4 Natural None 3.47 1.25 Inventive 4 Green None 3.53 0.78Inventive 4 Blue None 3.77 1.35 Inventive 5 Natural None 3.44 1.20Inventive 5 Natural HPN-20E 3.52 0.53 Inventive 5 Natural KSt 3.59 0.91Inventive 5 White None 3.77 1.17 Inventive 5 Green None 3.53 1.10Inventive 5 Red None 3.62 0.76 Inventive 5 White-2 None 3.69 1.18Inventive 5 Blue None 3.45 1.11 Inventive 5 Orange None 3.70 0.65Inventive 5 White HPN-20E 3.52 0.53 Inventive 5 Green HPN-20E 3.53 0.73Inventive 5 Red HPN-20E 3.59 0.59 Inventive 5 White-2 HPN-20E 3.63 0.39Inventive 5 Blue HPN-20E 3.50 0.56 Inventive 5 Orange HPN-20E 3.63 0.48Inventive 5 Green KSt 3.53 0.97 Inventive 5 Blue KSt 3.56 0.91 Inventive6 Natural None 3.48 1.10 Inventive 6 Green None 3.54 1.08 Inventive 6Blue None 3.65 1.09 Comparative A Natural None 3.57 1.39 Comparative AWhite None 3.38 1.22 Comparative A Blue None 3.39 1.24 Comparative AOrange None 3.93 0.91

1. A high-density polyethylene composition comprising: a firstcomponent, said first component being a high molecular weight ethylenealpha-olefin copolymer having a density in the range of 0.920 to 0.946g/cm³, and a melt index (I_(21.6)) in the range of 1 to 15 g/10 minutes;and a second component, said second component being a low molecularweight ethylene polymer having a density in the range of 0.965 to 0.980g/cm³, and a melt index (I₂) in the range of 30 to 1500 g/10 minutes;wherein said high-density polyethylene composition having a melt index(I₂) of at least 1 g/10 minutes, a density in the range of 0.950 to0.960 g/cm³; wherein said high-density polyethylene composition has a 1%secant modulus in psi of equal or greater to the following relationship:[(7,492,165*density (g/cm³))−6,975,000] psi/(g/cm³)); wherein saidhigh-density polyethylene composition has a molecular weightdistribution (Mw/Mn) from 5 to 13; and wherein said high-densitypolyethylene composition has a standard deviation of flow directionshrinkage of less than 7 percent across different colors.
 2. Thehigh-density polyethylene composition according to claim 1, wherein saidfirst component having a density in the range of 0.925 to 0.945 g/cm³.3. (canceled)
 4. The high-density polyethylene composition according toclaim 1, wherein said first component having a melt index (I_(21.6)) inthe range of 2 to 12 g/10 minutes.
 5. (canceled)
 6. The high-densitypolyethylene composition according to claim 1, wherein said secondcomponent having a density in the range of 0.965 to 0.975 g/cm³.
 7. Thehigh-density polyethylene composition according to claim 1, wherein saidsecond component having a melt index (I₂) in the range of 40 to 1300g/10 minutes.
 8. (canceled)
 9. (canceled)
 10. The high-densitypolyethylene composition according to claim 1, wherein said high-densitypolyethylene composition having a melt index (I₂) of at least 2 g/10minutes.
 11. The high-density polyethylene composition according toclaim 1, wherein said first component having a molecular weight in therange of 150,000 to 300,000.
 12. The high-density polyethylenecomposition according to claim 1, wherein said second component having amolecular weight in the range of 12,000 to 45,000.
 13. The high-densitypolyethylene composition according to claim 1, wherein said firstcomponent having a density in the range of 0.928 to 0.944 g/cm³, and amelt index (I_(21.6)) in the range of 2.5 to 11 g/10 minutes; whereinsaid second component having a density in the range of 0.965 to 0.975g/cm³, and a melt index (I₂) in the range of 50 to 1000 g/10 minutes.14. to
 16. (canceled)
 17. and
 18. (None originally due to numberingerror).
 19. A method of producing a high-density polyethylenecomposition comprising the steps of: introducing ethylene, and analpha-olefin comonomer into a first reactor; polymerizing said ethylenein the presence of said alpha-olefin comonomer in said first reactorthereby producing a first component, wherein said first component beinga high molecular weight ethylene alpha-olefin copolymer having a densityin the range of 0.920 to 0.946 g/cm³, and a melt index (I₂₁) in therange of 1 to 15 g/10 minutes; introducing said first component andadditional ethylene into a second reactor; polymerizing said additionalethylene in said second reactor thereby producing a second component,wherein said second component being a low molecular weight ethylenepolymer having a density in the range of 0.965 to 0.980 g/cm³, and amelt index (I₂) in the range of 30 to 1500 g/10 minutes; and therebyproducing said high-density polyethylene composition, whereinhigh-density polyethylene composition having a melt index (I₂) of atleast 1 g/10 minutes, a density in the range of 0.950 to 0.960 g/cm³:,wherein said high-density polyethylene composition has a 1% secantmodulus in psi of equal or greater to the following relationship:[(7,492,165*density (g/cm³))−6,975,000] psi/(g/cm³)); wherein saidhigh-density polyethylene composition has a molecular weightdistribution (Mw/Mn) from 5 to 13; and wherein said high-densitypolyethylene composition has a standard deviation of flow directionshrinkage of less than 7 percent across different colors.
 20. to 34.(canceled)
 35. and
 36. (None originally due to numbering error).
 37. to42. (canceled)
 43. A method of producing a manufactured articlecomprising an injection-molded bottle cap closure, the method comprisingthe steps of; injection molding said high-density polyethylenecomposition of claim 1 thereby forming said manufactured articlecomprising an injection-molded bottle cap closure, wherein theinjection-molded bottle cap closure comprises a skirt that axiallyextends from the periphery of a base, and internal screw threads forsecuring the cap to a container.
 44. to
 51. (canceled)